package com.soecode.wxtools.util.crypto;

import java.io.StringReader;
import java.nio.charset.Charset;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.SortedMap;
import java.util.TreeMap;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

/**
 * 对公众平台发送给公众账号的消息加解密示例代码.
 *
 * @copyright Copyright (c) 1998-2014 Tencent Inc.
 */

// ------------------------------------------------------------------------

/**
 * 针对org.apache.commons.codec.binary.Base64，
 * 需要导入架包commons-codec-1.9（或commons-codec-1.8等其他版本）
 * 官方下载地址：http://commons.apache.org/proper/commons-codec/download_codec.cgi
 */

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.codec.digest.DigestUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.xml.sax.InputSource;

/**
 * 加密工具【未完成，未测试，请勿使用】
 * @author antgan
 *
 */
public class WxCryptUtil {

	private static final Base64 base64 = new Base64();
	private static final Charset CHARSET = Charset.forName("utf-8");

	private static final ThreadLocal<DocumentBuilder> builderLocal=new ThreadLocal<DocumentBuilder>(){@Override protected DocumentBuilder initialValue(){try{return DocumentBuilderFactory.newInstance().newDocumentBuilder();}catch(ParserConfigurationException exc){throw new IllegalArgumentException(exc);}}};

	protected byte[] aesKey;
	protected String token;
	protected String appidOrCorpid;

	public WxCryptUtil() {
		super();
	}

	/**
	 * 构造函数
	 *
	 * @param token
	 *            公众平台上，开发者设置的token
	 * @param encodingAesKey
	 *            公众平台上，开发者设置的EncodingAESKey
	 * @param appidOrCorpid
	 *            公众平台appid/corpid
	 */
	public WxCryptUtil(String token, String encodingAesKey, String appidOrCorpid) {
		this.token = token;
		this.appidOrCorpid = appidOrCorpid;
		this.aesKey = Base64.decodeBase64(encodingAesKey + "=");
	}

	/**
	 * 将公众平台回复用户的消息加密打包.
	 * <ol>
	 * <li>对要发送的消息进行AES-CBC加密</li>
	 * <li>生成安全签名</li>
	 * <li>将消息密文和安全签名打包成xml格式</li>
	 * </ol>
	 *
	 * @param plainText
	 *            公众平台待回复用户的消息，xml格式的字符串
	 * @return 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce,
	 *         encrypt的xml格式的字符串
	 */
	public String encrypt(String plainText) {
		// 加密
		String encryptedXml = encrypt(genRandomStr(), plainText);

		// 生成安全签名
		String timeStamp = timeStamp = Long.toString(System.currentTimeMillis() / 1000l);
		String nonce = genRandomStr();

		try {
			String signature = SHA1.gen(token, timeStamp, nonce);
			String result = generateXml(encryptedXml, signature, timeStamp, nonce);
			return result;
		} catch (NoSuchAlgorithmException e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 对明文进行加密.
	 *
	 * @param plainText
	 *            需要加密的明文
	 * @return 加密后base64编码的字符串
	 */
	protected String encrypt(String randomStr, String plainText) {
		ByteGroup byteCollector = new ByteGroup();
		byte[] randomStringBytes = randomStr.getBytes(CHARSET);
		byte[] plainTextBytes = plainText.getBytes(CHARSET);
		byte[] bytesOfSizeInNetworkOrder = number2BytesInNetworkOrder(plainTextBytes.length);
		byte[] appIdBytes = appidOrCorpid.getBytes(CHARSET);

		// randomStr + networkBytesOrder + text + appid
		byteCollector.addBytes(randomStringBytes);
		byteCollector.addBytes(bytesOfSizeInNetworkOrder);
		byteCollector.addBytes(plainTextBytes);
		byteCollector.addBytes(appIdBytes);

		// ... + pad: 使用自定义的填充方式对明文进行补位填充
		byte[] padBytes = PKCS7Encoder.encode(byteCollector.size());
		byteCollector.addBytes(padBytes);

		// 获得最终的字节流, 未加密
		byte[] unencrypted = byteCollector.toBytes();

		try {
			// 设置加密模式为AES的CBC模式
			Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
			SecretKeySpec keySpec = new SecretKeySpec(aesKey, "AES");
			IvParameterSpec iv = new IvParameterSpec(aesKey, 0, 16);
			cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);

			// 加密
			byte[] encrypted = cipher.doFinal(unencrypted);

			// 使用BASE64对加密后的字符串进行编码
			String base64Encrypted = base64.encodeToString(encrypted);

			return base64Encrypted;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 检验消息的真实性，并且获取解密后的明文.
	 * <ol>
	 * <li>利用收到的密文生成安全签名，进行签名验证</li>
	 * <li>若验证通过，则提取xml中的加密消息</li>
	 * <li>对消息进行解密</li>
	 * </ol>
	 *
	 * @param msgSignature
	 *            签名串，对应URL参数的msg_signature
	 * @param timeStamp
	 *            时间戳，对应URL参数的timestamp
	 * @param nonce
	 *            随机串，对应URL参数的nonce
	 * @param encryptedXml
	 *            密文，对应POST请求的数据
	 * @return 解密后的原文
	 */
	public String decrypt(String msgSignature, String timeStamp, String nonce, String encryptedXml) {
		// 密钥，公众账号的app corpSecret
		// 提取密文
		String cipherText = extractEncryptPart(encryptedXml);

		try {
			// 验证安全签名
			String signature = SHA1.gen(token, timeStamp, nonce);
			if (!signature.equals(msgSignature)) {
				throw new RuntimeException("加密消息签名校验失败");
			}
		} catch (NoSuchAlgorithmException e) {
			throw new RuntimeException(e);
		}

		// 解密
		String result = decrypt(cipherText);
		return result;
	}

	/**
	 * 对密文进行解密.
	 *
	 * @param cipherText
	 *            需要解密的密文
	 * @return 解密得到的明文
	 */
	public String decrypt(String cipherText) {
		byte[] original;
		try {
			// 设置解密模式为AES的CBC模式
			Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
			SecretKeySpec key_spec = new SecretKeySpec(aesKey, "AES");
			IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(aesKey, 0, 16));
			cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);

			// 使用BASE64对密文进行解码
			byte[] encrypted = Base64.decodeBase64(cipherText);

			// 解密
			original = cipher.doFinal(encrypted);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}

		String xmlContent, from_appid;
		try {
			// 去除补位字符
			byte[] bytes = PKCS7Encoder.decode(original);

			// 分离16位随机字符串,网络字节序和AppId
			byte[] networkOrder = Arrays.copyOfRange(bytes, 16, 20);

			int xmlLength = bytesNetworkOrder2Number(networkOrder);

			xmlContent = new String(Arrays.copyOfRange(bytes, 20, 20 + xmlLength), CHARSET);
			from_appid = new String(Arrays.copyOfRange(bytes, 20 + xmlLength, bytes.length), CHARSET);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}

		// appid不相同的情况
		if (!from_appid.equals(appidOrCorpid)) {
			throw new RuntimeException("AppID不正确");
		}

		return xmlContent;

	}

	/**
	 * 微信公众号支付签名算法(详见:http://pay.weixin.qq.com/wiki/doc/api/index.php?chapter=
	 * 4_3)
	 * 
	 * @param packageParams
	 *            原始参数
	 * @param signKey
	 *            加密Key(即 商户Key)
	 * @param charset
	 *            编码
	 * @return 签名字符串
	 */
	public static String createSign(Map<String, String> packageParams, String signKey) {
		SortedMap<String, String> sortedMap = new TreeMap<String, String>();
		sortedMap.putAll(packageParams);

		List<String> keys = new ArrayList<String>(packageParams.keySet());
		Collections.sort(keys);

		StringBuffer toSign = new StringBuffer();
		for (String key : keys) {
			String value = packageParams.get(key);
			if (null != value && !"".equals(value) && !"sign".equals(key) && !"key".equals(key)) {
				toSign.append(key + "=" + value + "&");
			}
		}
		toSign.append("key=" + signKey);
		String sign = DigestUtils.md5Hex(toSign.toString()).toUpperCase();
		return sign;
	}

	/**
	 * 将一个数字转换成生成4个字节的网络字节序bytes数组
	 *
	 * @param number
	 */
	private byte[] number2BytesInNetworkOrder(int number) {
		byte[] orderBytes = new byte[4];
		orderBytes[3] = (byte) (number & 0xFF);
		orderBytes[2] = (byte) (number >> 8 & 0xFF);
		orderBytes[1] = (byte) (number >> 16 & 0xFF);
		orderBytes[0] = (byte) (number >> 24 & 0xFF);
		return orderBytes;
	}

	/**
	 * 4个字节的网络字节序bytes数组还原成一个数字
	 *
	 * @param bytesInNetworkOrder
	 */
	private int bytesNetworkOrder2Number(byte[] bytesInNetworkOrder) {
		int sourceNumber = 0;
		for (int i = 0; i < 4; i++) {
			sourceNumber <<= 8;
			sourceNumber |= bytesInNetworkOrder[i] & 0xff;
		}
		return sourceNumber;
	}

	/**
	 * 随机生成16位字符串
	 *
	 * @return
	 */
	private String genRandomStr() {
		String base = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
		Random random = new Random();
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < 16; i++) {
			int number = random.nextInt(base.length());
			sb.append(base.charAt(number));
		}
		return sb.toString();
	}

	/**
	 * 生成xml消息
	 *
	 * @param encrypt
	 *            加密后的消息密文
	 * @param signature
	 *            安全签名
	 * @param timestamp
	 *            时间戳
	 * @param nonce
	 *            随机字符串
	 * @return 生成的xml字符串
	 */
	private String generateXml(String encrypt, String signature, String timestamp, String nonce) {
		String format = "<xml>\n" + "<Encrypt><![CDATA[%1$s]]></Encrypt>\n"
				+ "<MsgSignature><![CDATA[%2$s]]></MsgSignature>\n" + "<TimeStamp>%3$s</TimeStamp>\n"
				+ "<Nonce><![CDATA[%4$s]]></Nonce>\n" + "</xml>";
		return String.format(format, encrypt, signature, timestamp, nonce);
	}

	static String extractEncryptPart(String xml) {
		try {
			DocumentBuilder db = builderLocal.get();
			Document document = db.parse(new InputSource(new StringReader(xml)));

			Element root = document.getDocumentElement();
			return root.getElementsByTagName("Encrypt").item(0).getTextContent();
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

}
